<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <link rel="stylesheet" href="btn.css">
</head>
<body>
    <!-- btn 负责按钮的通用样式 ,red teal orange(多态)多个类名 可继承-->
    <div class="btn">Hover me</div>
    <div class="btn red">Hover me</div>
    <div class="btn yellow">Hover me</div>
    <div class="btn teal">Hover me</div>
    <div class="btn orange">Hover me</div>

</body>
</html>